Nearly nine years after the Iraq War began, the U.S. is winding down its involvement there. U.S. troops will be out of Iraq by December 31st. The Obama administration says what comes next will be a new phase in the relationship with Iraq. What that involves will most likely be part of the discussion when Iraq's prime minister, Nouri al-Maliki, heads to Washington to meet with President Obama tomorrow.

NPR's Kelly McEvers reports from Baghdad.

KELLY MCEVERS, BYLINE: The invitation for Prime Minister Maliki to come to Washington was made in October when President Obama announced that all U.S. troops would be leaving Iraq for good.

PRESIDENT BARACK OBAMA: Today, I can say that our troops in Iraq will definitely be home for the holidays.

MCEVERS: That announcement came as a kind of surprise to Iraqis and Americans who'd expected the two sides reach some kind of agreement to allow a few thousands troops to remain in Iraq into next year. Analysts here in the region say Maliki and Obama might be discussing the question of inviting some troops back, mainly to work as trainers.

But questions remain about how many of these trainers would return, and how they'd be protected from prosecution under Iraqi law. This question of immunity is what caused talks between the U.S. and Iraq to break down before. The U.S. insists the Iraqi parliament should provide immunity for American soldiers. But some political groups here in Iraq - especially those backed by Iran - are against any troop presence. So the issue would be hard to pass in parliament.

Either way, the large combat presence - that at one time numbered more than 150,000 American soldiers here in Iraq - is now down to just a few thousand. Hundreds of soldiers and trucks are leaving every day.

Iraqis are mixed about the departure. Many, especially in the oil-rich, but ethnically divided city of Kirkuk, fear that violence could flare up again now that U.S. troops are leaving.

Kirkuk Governor Najmaldin Karim says the U.S. and Iraq should've tried harder to reach a deal for some American troops to stay.

GOVERNOR NAJMALDIN KARIM: We have made it clear months ago that some U.S. troops should stay in Iraq. And I honestly think that Iraqi government is at fault. But also, the U.S. government in a sense that they didn't push hard for this. I think there was no hard push.